interface PaymentStrategy {
    void pay(double amount);
}

class CreditCardPayment implements PaymentStrategy {
    private String name;
    CreditCardPayment(String name) { this.name = name; }

    public void pay(double amount) {
        System.out.println(name
            + " paid $" + amount + " with Credit Card");
    }
}

class PayPalPayment implements PaymentStrategy {
    private String email;
    PayPalPayment(String email) { this.email = email; }

    public void pay(double amount) {
        System.out.println(email
            + " paid $" + amount + " with PayPal");
    }
}

class BitcoinPayment implements PaymentStrategy {
    private String wallet;
    BitcoinPayment(String wallet) { this.wallet = wallet; }

    public void pay(double amount) {
        System.out.println(wallet
            + " paid $" + amount + " with Bitcoin");
    }
}

class ShoppingCart {
    private PaymentStrategy strategy;

    void setPaymentStrategy(PaymentStrategy strategy) {
        this.strategy = strategy;
    }

    void checkout(double amount) {
        strategy.pay(amount);
    }
}

public static void main(String[] args) {
    ShoppingCart cart = new ShoppingCart();

    cart.setPaymentStrategy(
        new CreditCardPayment("Alice"));
    cart.checkout(100.0);

    cart.setPaymentStrategy(
        new PayPalPayment("alice@example.com"));
    cart.checkout(50.0);
}